Torsion-spring for clocks, watches, etc.



Patented Oct. 1"], 1933 UNITED STATES TORSION -SPR1NG FOR CLOCKS,WATCHES,

ETC.

Thomas H. Chamberlain, New Haven, Conn., as-

' signor to The New Haven Clock Company,

New Haven, Conn., a corporation No Drawing. Application March 17, 1930Serial No. 436,650

2 Claims. (Cl. 75-1) This invention relates to an improvement intorsion-springs for various measuring or indicating instruments-ofprecision, such as clocks, watches, ammeters, .voltmeters, and other in-5 struments in which a variation in the modulus of elasticity of thetorsion-springs, due to, thermal changes, is a factor affectingaccuracy.

The main object of my invention is to produce a torsion-spring whichwill have a substantially-uniform modulus of elasticity throughout thenormal range of atmospheric temperatures, whereby thermal changes willnot appreciably affect the precision of the readings of an instrument inwhich my improved torsionspring is installed.

A further object of my invention is to produce a torsion-spring having asubstantially-uniform modulus of elasticity throughout the normal rangeof atmospheric temperatures, and which 0 is sufliciently ductile to bereadily drawn, rolled,

or otherwise formed and shaped.

A further object of my invention is to produce a torsion-springcharacterized as above which will be highly resistant to corrosion.

With the above and other objects in view, as will appear from thefollowing, my invention consists in a torsion-spring having asubstantially-uniform modulus of elasticity throughout the normal rangeof atmospheric temperatures and consisting of an alloy hereinafterdescribed.

My improved torsion-spring is preferably made from a ferrous alloy ofthe following composi- 'tion:

Per cent Carbon 0. 15 to 0. 17 Manganese 0. 70 to 0. 90 Silicon 0. 65 to0. 80 Nickel 35. 50 to 36. 50 Chromium 12. 00 to 13. 00

Iron to form the balance after a suitable allowance for impurities, suchas sulphur, phosphorous, etc. 7

The carbonand manganeseand siliconcontent set forth above act ashardeners, and

while they, in the aggregate, are appreciably high, it will be notedthat no single one of them is sufliciently high to occasion brittleness,which might result, were a single hardener to be employed. For instance,by employing both 0 manganese and silicon, in addition to carbon, tosecure the desired hardness, the carbon may be kept at such a smallpercentage as not to occasion any appreciable formation ofchromecarbides.

A torsion-spring composed of my improved alloy is not only comparativelyeasy to form, but its tension is so nearly uniform, despite normalthermal changes, that when employed as a balanceor hair-spring in awatch or clock it insures substantially-uniform impulses to thebalance-wheel oi the time-piece with which it is employed, so that allother variable factors hav- 'ing been provided for, approximatelyperfect Per cent Nickel 34. to 37. 50 Chromium 11. 00 to 13. 00Manganese ,0. to 1.00 Silicon I 0. 25 to 0.90 Carbon 0. 0'7 to 0. 35

Iron forming substantially all of the balance 2. A torsion-springcombining high elastic limit, ductility and a substantially-uniformmodulus of elasticity comprising the following elements within theranges given: t

- Per cen Nickel 35. 50 to 36. 50 Chromium 11. 50 to 12; 50 Manganese 0.'70 to 0. 90 Silic 0. to 0. 80 Carbon 0. 07 to 0. 17

Iron forming substantially all of the balance THOMAS H. CHAIMBERLAIN.

